Birther!!!!! No credibility, right????!!!
If he was a citizen at birth then he is a natural born citizen.
The Obama issue came down to the age of his mother at the time and the law the required her to be of a of an age to provide birth right citizenship. see
http://www.state.gov/documents/organization/86757.pdf
As well as the good possibility that he renounced his citizenship or committed fraud at Columbia IF he applied as a foreign student